The present invention relates to a roof underlayment sheet material which is interposed between a combustible roof deck or substrate of a structure and a bottom surface of a roofing membrane such as a single ply, modified bitumen, built-up roof, or a metal standing-seam roof. Optional insulation may also be between this underlayment sheet material and bottom surface of roofing membrane. The underlayment sheet material provides both resistance to water and retardant effect to the spread of fire. Additionally, it may provide a temporary waterproofing roof membrane without any other membrane material.
In the construction industry, it is customary to provide a structure with an outer layer of protection against fire and weather. Typically, the outermost layer of the structure will be inherently fire and weather resistant. Most commonly these layers include brick or siding used on walls and metal, and metal, rubber, or bitumen based roofing systems used on roof decks. However, it is just as typical for the structural layer immediately below this outermost layer to comprise wood or another combustible material. It has become customary to interpose an underlayment between these two layers to enhance the protection of the structure, typically against moisture, vapor drive, water, and in some cases particularly, against fire. In addition to the resistance to these elements, it is also important that the underlayment sheet material be dimensionally stable under a variety of moisture and temperature conditions to be acceptable.
It is clearly desirable to achieve a xe2x80x9cClass Axe2x80x9d fire rating in a roofing membrane structure, as defined by Underwriters Laboratories Inc., with such an underlayment sheet material, as this permits construction without use of a barrier board layer, such as a gypsum barrier board. These barrier boards typically come in 4xe2x80x2 by 4xe2x80x2 or 4xe2x80x2 by 8xe2x80x2 board stock. Applying such a barrier board layer requires much more time than applying a rolled sheet material. It is also clearly desirable to be able to provide a temporary roof membrane to a structure so that water resistance is immediately provided even before the final roofing surface is applied.
Certain materials are known and useful as underlayment sheet materials for side walls and roofs. These include TYVEK, a spun-bonded polyolefin sheet material commercially available from E.I. duPont and Co. and tar paper, which is available from a variety of vendors. These underlayment sheet materials provide significant resistance against moisture, water, and vapor drive, but they offer little to no resistance to fire, and, in fact, present a fire hazard once ignited. There are also underlayment sheets which provide fire resistance but have no resistance to moisture, water, or vapor drive. These include the sheet material sold commercially as MANNIGLAS by the Manning Division of Lydall, Inc., Troy, N.Y. While the vendors of this type of material claim that it diverts water flow, there is no claim made as to preventing water intrusion.
As a result, it is a still unmet desire of the prior art to provide a self-adhering, moisture resistant, water resistant, and vapor drive resistant, fire retardant underlayment sheet material for a roofing deck.
It is therefore an advantage of the present invention to create an underlayment sheet material suitable for roofing and other applications that has the typical properties of being moisture resistant, water resistant, and vapor drive resistant with fire resistance. It is particularly desirable to combine these features with a pressure-sensitive adhesive coating on a lower face of the sheet. This invention is a membrane sheet material that consists of an inner core or reinforcement coated with bitumen creating a waterproof membrane. It is also desirable to provide an upper face of the sheet with a weathering surface. The membrane sheet material comes in a roll form which is unrolled for application and comes in typical lengths of 25 to 40 feet in length.
In a particular embodiment, the sheet material useful as a waterproof underlayment for a roof of a structure and having an upper and a lower surface comprises a web of reinforcing mat comprising fire-resistant fibers and a continuous non-porous matrix of water-resistant modified bitumen saturating the web of reinforcing mat; wherein the modified bitumen is self-adhesive. In such an embodiment, the reinforcing mat, having a density in the range of about 4 lbs/100 ft2 comprises glass fibers. Further, the reinforcing mat is a non-woven mat of the glass fibers, held together by a dry binder adhesive. In many embodiments, the modified bitumen is an asphalt modified by a rubbery block co-polymer selected from the group consisting of: styrene-butadiene-styrene (xe2x80x9cSBSxe2x80x9d), styrene-isoprene-styrene (xe2x80x9cSISxe2x80x9d) and a combination of SBS and SIS. In such embodiments, the modified bitumen has a ring and ball softening point of at least about 215 F when measured under ASTM Method D36. The modified bitumen also has a penetration of about 45 dmm when measured under ASTM Method D5 and a low temperature flexibility of 50 mil film at 0xc2x0, as well as a viscosity of about 6800 cPs when measured at 350xc2x0 F. under ASTM Method D4022. In the embodiments, the modified bitumen further comprises a tackifier, a plasticizing/process oil, an anti-oxidant and a ultraviolet stabilizer. Such a modified bitumen comprises about 80% by weight asphalt and rubbery block co-polymer, about 14.5% hydrocarbon resin, and about 5% naphthenic oil, with the anti-oxidant and ultraviolet stabilizers comprising the balance at less than 0.5%.
The sheet material will generally have its upper surface coated with a granular material, especially a coal slag aggregate.
The sheet material""s lower surface has sufficient peel strength to adhere the sheet material in a waterproof manner.
The sheet material exhibits a Class A fire rating when measured ASTM Method E108 over a combustible deck.